The invention concerns plates or sheets of Al alloys involving structural hardening and having a continuous variation in the properties of use in at least one given direction (D) whatever and a process and an apparatus for producing same.
In general the attempt in metallurgy is to obtain products whose properties are as homogenous as possible throughout the entire volume thereof.
However for some uses it is desirable to produce products whose properties, with a given chemical composition, vary continuously in at least one given direction (D).
For example, in a bee which is subjected to flexural forces and to fatigue it is desirable for the part which is under compression to have a high level of mechanical resistance to compression while the part subjected to tensile stress must be resistant to damage, in particular being of a lower level of hardness.
Likewise in a shock absorber it is desirable for the impact zone to be resilient and ductile whereas the opposite part must withstand the force applied.
More generally that problem arises in all situations where the product is subjected in service either to a severe gradient in terms of mechanical stresses or to heterogenous conditions of use (for example resistance to corrosion).